This invention relates to heat-recoverable articles in general, and more particularly to heat-recoverable articles that can be positioned around cables, pipes, connectors or the like, wherein the articles disposed therein may be easily communicated with after heat-recovery.
Ellis, U.S. Pat. No. 3,455,336, describes a device for sealing, insulating or acting as a protective closure member for elongated objects such as cables, pipes or the like where the ends of the elongated objects are not accessible, or where it is undesirable to disconnect or otherwise displace them from their original position. A particular embodiment of Ellis includes a heat-recoverable article having a stem and a pair of communicating arms accommodating a branch-off between electric cables. This embodiment can be used for a branch-off from a main cable to provide access to the wires of the branch-off after installation of the closure member. However, during certain operations this structure proves cumbersome and in general does not offer the user a sufficiently flexible means of accessing the contents disposed in the article after heat-recovery.
As is quite well known in the art, one cannot make openings in heat-recoverable material without experiencing crack propagation during heat recovery. In the usual case, even a small nick or cut in the material results in splitting of a heat-recovered sleeve. Openings in heat-recoverable material cause a build-up of unresolved recovery forces. These forces build up quite rapidly due to the nature of the heat-recoverable material. As a result of this build-up crack propagation occurs causing the heat-recoverable material to split and consequently fail.
In the past, others have attempted to use a partially heat-recoverable tubular member which included a non-heat-recoverable portion immediately adjacent the opening. It was hoped that crack propagation would not occur during heat recovery because the immediate area surrounding the opening was not heat-recoverable. However, it was found that hot-spots developed causing crack propagation. In addition, such material is generally unreliable as well as expensive and difficult to manufacture.
Applicants herein have developed a heat-recoverable closure device including a heat-recoverable tubular member having at least one opening in the area where the member is heat-recoverable. The device further includes a compression means for preventing crack propagation caused by unresolved recovery forces around the opening. The compression means is attached generally normal to that part of the tubular member adjacent each opening and constantly maintained in compression during heat-recovery. The means thereby exerts a force generally normal to and radially against the tubular member for equalizing unresolved recovery forces on that portion of the member adjacent the opening, thereby preventing crack propagation during heat-recovery.